Gallatabenzene Ligands Emerging from Open Lutetocene and Yttrocene Methyl Complexes.

Utilizing ternary mixtures [LnMe]/K(2,4-dtbp)/GaMe (Ln=Lu, Y; 2,4-dtbp=2,4-di-tert-butyl-pentadienyl), a series of metallacycles is accessible via tandem salt metathesis/deprotonation. Depending on the precursor molar ratio, both gallatabenzene and lutetacyclic moieties with fully planar metallacycles are obtained, which were further analyzed using DFT calculations. The precursor molar ratio affects the extent of pentadienyl C-H-bond activation and oligomerization to tetra- and pentametallic arrays.

A Terminal Yttrium Phosphinidene.

Terminal, nondirectional ionic "multiple" bond interactions between group 15 elements and rare-earth metals (Ln) have remained a challenging target until present. Although reports on terminal imide species have accumulated in the meantime, examples of terminal congeners with the higher homologue phosphorus are yet elusive. Herein, we present the synthesis of the first terminal yttrium organophosphinidene complex, TpY(═PCHPr-2,6)(DMAP), according to a double-deprotonation sequence previously established for organoimides of the smaller rare-earth metals.

Schlenk's Legacy-Methyllithium Put under Close Scrutiny.

Commercially available stock solutions of organolithium reagents are well-implemented tools in organic and organometallic chemistry. However, such solutions are inherently contaminated with lithium halide salts, which can complicate certain synthesis protocols and purification processes. Here, we report the isolation of chloride-free methyllithium employing K[N(SiMe ) ] as a halide-trapping reagent.

Molecular Ln(III)-H-E(II) Linkages (Ln=Y, Lu; E=Ge, Sn, Pb).

Following the alkane-elimination route, the reaction between tetravalent aryl tintrihydride Ar*SnH and trivalent rare-earth-metallocene alkyls [Cp* Ln(CH{SiMe } )] gave complexes [Cp* Ln(μ-H) SnAr*] implementing a low-valent tin hydride (Ln=Y, Lu; Ar*=2,6-Trip C H , Trip=2,4,6-triisopropylphenyl). The homologous complexes of germanium and lead, [Cp* Ln(μ-H) EAr*] (E = Ge, Pb), were accessed via addition of low-valent [(Ar*EH) ] to the rare-earth-metal hydrides [(Cp* LnH) ]. The lead compounds [Cp* Ln(μ-H) PbAr*] exhibit H/D exchange in reactions with deuterated solvents or dihydrogen.

Open-Shell Early Lanthanide Terminal Imides.

Group 3- and 4f-element organometallic chemistry and reactivity are decisively driven by the rare-earth-metal/lanthanide (Ln) ion size and associated electronegativity/ionicity/Lewis acidity criteria. For these reasons, the synthesis of terminal "unsupported" imides [Ln═NR] of the smaller, closed-shell Sc(III), Lu(III), Y(III), and increasingly covalent Ce(IV) has involved distinct reaction protocols while derivatives of the "early" large Ln(III) have remained elusive. Herein, we report such terminal imides of open-shell lanthanide cations Ce(III), Nd(III), and Sm(III) according to a new reaction protocol.

Hydridoorganostannylene Coordination: Group 4 Metallocene Dichloride Reduction in Reaction with Organodihydridostannate Anions.

Organodihydridoelement anions of germanium and tin were reacted with metallocene dichlorides of Group 4 metals Ti, Zr and Hf. The germate anion [Ar*GeH ] reacts with hafnocene dichloride under formation of the substitution product [Cp Hf(GeH Ar*) ]. Reaction of the organodihydridostannate with metallocene dichlorides affords the reduction products [Cp M(SnHAr*) ] (M=Ti, Zr, Hf).

Gallium Methylene.

Despite the eminent importance of metal alkylidene species for organic synthesis and industrial catalytic processes, molecular homoleptic metal methylene compounds [M(CH ) ] as the simplest representatives, have remained elusive. Reports on this topic date back to 1955 when polymeric [Li (CH )] and [Mg(CH )] were accessed by pyrolysis of methyllithium and dimethylmagnesium, respectively. However, the insoluble salt-like composition of these compounds has impeded their application as valuable reagents.

Cyclic Distannene or Bis(stannylene) with a Ferrocenyl Backbone: Synthesis, Structure, and Coordination Chemistry.

1,1'-Dilithioferrocene was reacted with 2 equiv of isopropyl (Ar*) or methyl (Ar') substituted terphenyl tin(II) chloride. Reaction product 1, carrying the bulkier terphenyl substituent Ar*, displays a bis(stannylene) structure in the solid state without formation of a tin-tin bond. Temperature-dependent solution Sn NMR spectroscopy, however, revealed a dynamic interplay between bis(stannylene) (100 °C) and cyclic distannene (-80 °C).

Synthesis and structural diversity of trivalent rare-earth metal diisopropylamide complexes.

A series of rare-earth metal diisopropylamide complexes has been obtained via salt metathesis employing LnCl3(THF)x and lithium (LDA) or sodium diisopropylamide (NDA) in n-hexane. Reactions with AM : Ln ratios ≥3 gave ate complexes (AM)Ln(NiPr2)4(THF)n (n = 1, 2; Ln = Sc, Y, La, Lu; AM = Li, Na) in good yields. For smaller rare-earth metal centres such as scandium and lutetium, a Li : Ln ratio = 2.

Binuclear complexes of Ni(I) from 4-terphenyldithiophenol.

Binuclear complexes of Ni(i) have been prepared from a 4-terphenyldithiophenol ligand. Steric effects were found to determine the formation of coordination isomeric structures that differ in the nature of metal-to-ligand bonding. Coordination of spatially demanding phosphine ligands PR3, R = C6H6, C6H11, at nickel sites results in a butterfly shaped thiolate-bridged Ni2(μ-S)2 motif.

Comparison of hydrogen elimination from molecular zinc and magnesium hydride clusters.

In analogy to the previously reported tetranuclear magnesium hydride cluster with a bridged dianionic bis-β-diketiminate ligand, a related zinc hydride cluster has been prepared. The crystal structures of these magnesium and zinc hydride complexes are similar: the metal atoms are situated at the corners of a tetrahedron in which the vertices are bridged either by dianionic bis-β-diketiminate ligands or hydride ions. Both structures are retained in solution and show examples of H(-)⋅⋅⋅H(-) NMR coupling (Mg: 8.

A dimethylgallium boryl complex and its methyllithium addition compound.

The three-coordinate complex Me2Ga[B(NArCH)2] (Ar = C6H3iPr2-2,6) is accessible via a tandem Lewis acid-base metathesis protocol employing (THF)2Li[B(NArCH)2] and GaMe3. It features a very short Ga-B bond of 2.067(3) Å, which was further investigated by DFT calculations and the analysis of the electron density.

Is There BN Bond-Length Alternation in 1,2:3,4:5,6-Tris(biphenylylene)borazines?

The alternation of the BN bonds in the central borazine ring of the overcrowded 1,2:3,4:5,6-tris(biphenylylene)borazine (2 a) and its tribromo derivative (2 g) is investigated by computational methods and compared with their experimentally obtained crystal structures. The calculations are performed with a meta-generalized-gradient-approximation (GGA) density functional (Tao-Perdew-Staroverov-Scuseria (TPSS)) without and with dispersion corrections, including Becke-Johnson damping, in conjunction with a polarized triple-ζ basis set. These data show a small bond-length alternation (BLA) of around 0.

Well-defined molecular magnesium hydride clusters: relationship between size and hydrogen-elimination temperature.

A new tetranuclear magnesium hydride cluster, [{NN-(MgH)2}2], which was based on a N-N-coupled bis-β-diketiminate ligand (NN(2-)), was obtained from the reaction of [{NN-(MgnBu)2}2] with PhSiH3. Its crystal structure reveals an almost-tetrahedral arrangement of Mg atoms and two different sets of hydride ions, which give rise to a coupling in the NMR spectrum (J = 8.5 Hz).

Non-classical hydrogen bonding in [K(1-aza-18-crown-6)]BH4 and its 18-crown-6 counterpart.

The extended structures of [K(1-aza-18-crown-6)]BH(4) and its 18-crown-6 analogue exhibits significantly different primary and secondary stabilizing interactions. However, their respective ion pairs display similar cation-to-anion interactions, in spite of the differences in the nature of the crown ether ligand.

Insights into metal borohydride and aluminohydride bonding: X-ray and neutron diffraction structures and a DFT and charge density study of [Na(15-crown-5)][EH(4)] (E = B, Al).

The neutron and X-ray structures of [Na(15-crown-5)][BH(4)] and [Na(15-crown-5)][AlH(4)], respectively, are reported, along with a topological analysis of their DFT-computed charge densities that explores the bonding between the anionic complex hydride [EH(4)](-) (E = B, Al) and the counterion [Na(15-crown-5)](+). In each case, the interaction is weak and mainly electrostatic in nature; however, notable differences are observed in the manner in which [BH(4)](-) and [AlH(4)](-) bind to the metal, which explains their different coordination modes. A range of unconventional E-H···H-C contacts is revealed to play an important role in the overall bonding and crystal packing of both complexes.

Can P-H sigma-bond complexes be prepared? A computational study by DFT and AIM methods.

A series of complexes of general formula [CpMn(CO)(2)(eta(2)-HPR(1)R(2).BCl(3))] has been studied by DFT calculations and topological analyses of the charge density thus derived. The 21 complexes included in this study exhibit closely similar Mn-H-P geometries, in spite of a wide range of substituents (R(1); R(2)) at the phosphorus atom.

A structural study of [CpM(CO)3H] (M = Cr, Mo and W) by single-crystal X-ray diffraction and DFT calculations: sterically crowded yet surprisingly flexible molecules.

The single-crystal X-ray structures of the complexes [CpCr(CO)3H] 1, [CpMo(CO)3H] 2 and [CpW(CO)3H] 3 are reported. The results indicate that 1 adopts a structure close to a distorted three-legged piano stool geometry, whereas a conventional four-legged piano stool arrangement is observed for 2 and 3. Further insight into the equilibrium geometries and potential energy surfaces of all three complexes was obtained by DFT calculations.

Nature of the bonding in metal-silane sigma-complexes.

The nature of metal silane sigma-bond interaction has been investigated in several key systems by a range of experimental and computational techniques. The structure of [Cp'Mn(CO)(2)(eta(2)-HSiHPh(2))] 1 has been determined by single crystal neutron diffraction, and the geometry at the Si atom is shown to approximate a trigonal bipyramid; salient bond distances and angles are Mn-H(1) 1.575(14), Si-H(1) 1.

Cationic rare-earth metal SALEN complexes.

Complexes (Salpren(tBu,tBu))Y[N(SiHMe2)2](thf) and (SALEN(tBu,tBu))La[N(SiHMe2)2](thf) (SALEN(tBu,tBu) = Salcyc(tBu,tBu) and Salpren(tBu,tBu)) were prepared from Ln[N(SiHMe2)2]3(thf)2 and H2SALEN(tBu,tBu). The yttrium complex was characterized by X-ray crystallography revealing intrinsic solid-state structural features: the metal centre is displaced by 1.05 angstroms from the [N2O2] least squares plane of a highly bent Salpren(tBu,tBu) ligand (angle(Ph,Ph) dihedral angle of 80.

Homoleptic rare-earth metal(III) tetramethylaluminates: structural chemistry, reactivity, and performance in isoprene polymerization.

The complexes [Ln(AlMe4)3] (Ln=Y, La, Ce, Pr, Nd, Sm, Ho, Lu) have been synthesized by an amide elimination route and the structures of [Lu{(micro-Me)2AlMe2}3], [Sm{(micro-Me)2AlMe2}3], [Pr{(micro-Me)2AlMe2}3], and [La{(micro-Me)2AlMe2}2{(micro-Me)3AlMe}] determined by X-ray crystallography. These structures reveal a distinct Ln3+ cation size-dependency. A comprehensive insight into the intrinsic properties and solution coordination phenomena of [Ln(AlMe4)3] complexes has been gained from extended dynamic 1H and 13C NMR spectroscopic studies, as well as 1D 89Y, 2D 1H/89Y, and 27Al NMR spectroscopic investigations.

Elucidation of the bonding in Mn(eta2-SiH) complexes by charge density analysis and T1 NMR measurements: asymmetric oxidative addition and anomeric effects at silicon.

The bonding in Mn(eta2-SiH) complexes is interpreted in terms of an asymmetric oxidative addition whose extent is controlled by the substitution pattern at the hypercoordinate silicon centre, and especially by the ligand trans to the eta2-coordinating SiH moiety.

Synthesis and structural characterization of scandium SALEN complexes.

A series of heteroleptic scandium SALEN complexes, [(SALEN)Sc(mu-Cl)]2 and (SALEN)Sc[N(SiHMe2)2] is obtained via amine elimination reactions using [Sc(N(i)Pr2)2(mu-Cl)(THF)]2 and Sc[N(SiHMe2)2]3(THF) as metal precursors, respectively. H(2)SALEN ligand precursors comprising H2Salen [(1,2-ethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol], H2Salpren [(2,2-dimethylpropanediyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol], H2Salcyc [(1R,2R)-(-)-1,2-cyclohexanediyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol] and H2Salphen [((1S,2S)-(-)-1,2-diphenylethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol] are selected according to solubility and ligand backbone variation ("=N-(R)-N=" bite angle) criteria. Consideration is given to the feasibility of [Cl --> NR2] and [N(SiHMe2)2--> OSiR3] secondary ligand exchange reactions.

Ruthenium trihydrides with N-heterocyclic carbene ligands: effects on quantum mechanical exchange coupling.

Ruthenium trihydrides containing N-heterocyclic carbene ligands display large quantum mechanical exchange couplings in their 1H NMR spectra: DFT calculations are used to explore this phenomenon and to compare them to their phosphine congeners.